The purpose of this proposal is to determine the aggregation mechanism of bovine alpha-crystallin and human lens proteins and therefore, to gain insight into the development of senile nuclear cataracts. One feasible approach to delineating the mechanism whereby subunits aggregate is through the isolation and characterization of intermediate sized aggregates of alpha-crystallin that can be produced by chemical modification. The minimal number of acidic and basic polypeptides in the aggregates can be determined to ascertain the building blocks or the promoters for the aggregation of alpha- crystallin. Such results will also provide insight for investigating the formation of giant protein aggregates that accompany the opacification of human cataractous lenses. Various chromatographic procedures will be employed in the separation and purification of these intermediates. Conformation and size distribution of these aggregates will be analyzed using spectropolarimetry and the ultracentrifuge. The role of the minor non- proteinous components in determining the size of the alpha-crystallin aggregates also will be studied with thin layer and gas-liquid chromatography.